Barrier walls that are formed from a plurality of elongated piles typically are driven into the earth to a depth sufficient to support the panels in an upright attitude. In some cases, the piles are in the form of extruded structural panels and are formed with male and female opposed edges so that similar panels can be locked together at their adjacent edges to form a continuous barrier wall. Because of the strength required of the panels when being driven into the earth and the strength required under load conditions, the panels have been made of steel or aluminum.
In recent years, structural panels have been constructed of polyvinylchloride and other plastics having relatively low tensile and high compression strengths. The panels are extruded in a continuous manufacturing process, and in order to provide the strengths in the panel necessary to withstand the loads that are expected to be applied to the panels, the thicknesses of the panels have been increased over the typical thickness of similar panels formed of steel or aluminum. For example, the modulus of elasticity of polyvinylchloride ("PVC") is estimated at 400,000 psi, whereas the modulus of elasticity of aluminum and steel is estimated at 10,000,000 psi and 30,000,000 to 40,000,000 psi respectively. Therefore, for PVC to achieve the strength characteristics of aluminum, for example, the PVC would be required to be approximately 25 times thicker than the aluminum.
In order to produce a structural panel formed of a synthetic resin that is to be used as a driven pile in the formation of a barrier wall, the panels have been formed in various strengthening cross sectional shapes, such as V shapes, Z shapes, U shapes, etc. so as to provide resistance to bending in response to the application of axial and/or lateral loads to the panels. Further, the panels have been constructed so as to have at their opposite edges male and female locking elements, so that the edge of one panel locks with and supports the edge of an adjacent panel. An example of this type of product is disclosed in U.S. Pat. No. 5,145,287.
After the first panels have been driven into place, subsequent panels can be driven into place adjacent the previously driven panels, by telescopically sliding the female locking element at the edge of the to be driven panels about the exposed male locking element of the previously driven panel, and progressively driving the panels into the earth as the telescoped locking elements progressively guide the panels into place.
The panels usually are from 2-40 feet in length, and while the shapes of the panels are very important in resisting the axial and lateral forces applied to the panels during the driving function, the lower, outer corner of the panels being driven are most vulnerable to bending forces and is most likely to become deformed during the driving procedure. Although it might be apparent that the distal locking element could be increased in size so as to include enough material to better resist the forces being applied during the driving of the structural panel, the increased thickness of the panel increases the likelihood that the panel will be misshapened during the production process. It is important that the panel be of substantially uniform thickness throughout its entire width so as to cool evenly after it has been extruded, so that warping of the panel will not occur. Therefore, it is impractical to add thickness to the panel at or adjacent the male locking element without affecting the production process and/or the shape of the finished panel.
Therefore, it would be desirable to provide a structural panel for forming barrier walls and the like which can be driven as a pile into the earth, and which would have sufficient strength to withstand the vertical driving forces and the lateral forces that are to be applied to the panel during driving of the panel and after the panel has been placed in its desired position, while minimizing the amount of material in the panel and while forming a panel of symmetrical and uniform thickness shape.